U.S. patent number 4,308,485 [Application Number 06/018,848] was granted by the patent office on 1981-12-29 for shadow mask support in a color cathode ray tube.
This patent grant is currently assigned to Videocolor, S. A.. Invention is credited to Cormio Ignazio.
United States Patent |
4,308,485 |
Ignazio |
December 29, 1981 |
Shadow mask support in a color cathode ray tube
Abstract
A shadow-mask cathode ray tube for the visualization of colors,
such as in television, where the peripheral edge of the mask is
rigid with the frame fixed on the tube plate and is in contact with
said frame only in areas spaced from each other. The frame is
formed with bosses providing its contact in reduced cross-section
areas spaced from each other with the edge of the mask.
Inventors: |
Ignazio; Cormio (Rome,
IT) |
Assignee: |
Videocolor, S. A.
(FR)
|
Family
ID: |
9205701 |
Appl.
No.: |
06/018,848 |
Filed: |
March 8, 1979 |
Foreign Application Priority Data
|
|
|
|
|
Mar 13, 1978 [FR] |
|
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78 07191 |
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Current U.S.
Class: |
313/407 |
Current CPC
Class: |
H01J
29/073 (20130101); H01J 31/201 (20130101); H01J
2229/0772 (20130101); H01J 2229/0722 (20130101); H01J
2229/0716 (20130101) |
Current International
Class: |
H01J
31/20 (20060101); H01J 29/07 (20060101); H01J
31/10 (20060101); H01J 029/07 () |
Field of
Search: |
;313/407,405,406,404,402 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Demeo; Palmer C.
Attorney, Agent or Firm: Kane, Dalsimer, Kane, Sullivan and
Kurucz
Claims
I claim:
1. In a colour cathode ray-tube having a plate and a shadow mask
mounted behind said plate, the combination of a shadow mask having
a light grid face formed integrally with a rearwardly extending
peripheral wall edge substantially rectangular in shape and a rigid
frame secured to said plate comprising a substantially rectangular
skirt having a front and rear edge with said skirt substantially
parallel to and fitting with said wall edge of the mask, said wall
edge of the mask and said skirt of the frame being secured to one
another by a plurality of welding points spaced from each other,
said skirt comprises a plurality of bosses spaced apart therearound
which provide contact of said skirt with said wall edge along a
plurality of areas of limited extent at spaced apart locations
therearound, said bosses extend only part of the distance between
said front and rear edge and protrude inwardly of said skirt
adjacent to said rear edge thereof, said wall edge extending
between a peripheral line around said light grid face and a
rearward edge thereof, and said wall edge contacts said bosses near
said rearward edge to leave a contactless peripheral zone between
said skirt and said wall edge next to said peripheral line.
2. A shadow mask colour cathode ray tube having an axis and
comprising a shadow mask having a light grid face formed integrally
with a peripheral substantially rectangular wall edge extending in
a direction substantially parallel to the axis of the tube
rearwardly of said light grid face, and a rigid frame comprising a
substantially rectangular skirt substantially parallel and secured
to said wall edge of the mask, said skirt having a plurality of
spaced apart inwardly protruding bosses therearound, wherein said
wall edge contacts said bosses along a plurality of respective
spaced apart areas rearwardly adjacent said edge to leave a
peripheral area of said wall edge adjacent said light grid face
free of contact with said skirt.
3. A tube according to claim 2, wherein said skirt has a front and
a rear boundary spaced in a direction substantially parallel to
said axis and said bosses are located adjacent said rear boundary
and have an extent parallel to said axis less than the distance
between said front and rear boundary to leave a contactless zone on
said skirt opposite said peripheral area of said wall edge at a
short distance therefrom.
4. A tube according to claim 3 further comprising a plurality of
welding points to secure said wall edge to said skirt at the
location of said bosses.
Description
The invention relates to a cathode ray tube of the shadow-mask type
for the visualization of colours, particularly in television.
It is known that the colour television tubes have, in the vicinity
of the plate, that is in the frontal portion of the tube on which
are deposited the phosphors, a mask made for instance of a metallic
plate or grid of about 1/10th of mm in thickness comprising a
grating with openings of oblong shape or other. Opposite each of
said openings are three areas, of small surfaces, of the phosphors
layer; said areas assume when they are excited respectively the
green, red and blue colours. The relative positions of the electron
guns, of the mask openings and of the areas of the phosphors layer
as well as the control means for the beams generated by the guns
are such that each of said electron guns can only excite the
phosphors of a determined colour.
The position of the mask relative to the phosphors, that is
relative to the plate, should therefore be fixed with the greatest
precision for a good operation of the tube, and this whatever the
operation conditions of the tube. It is therefore necessary to take
particular precautions so that said relative position is not
changed when the mask heats up under the effect of the electrons
projected by the guns.
In a known tube, the mask is fixed by a peripheral edge to a frame,
said edge being formed with bosses and being in contact with the
frame through said bosses. The frame is rigid with the plate
through fixation means which are specially adapted for minimizing
the heating consequences of the mask on its position relative to
the plate.
The object of the invention is to reduce still more the effects of
the temperature variations of the mask on its position relative to
the plate.
A further object of the invention is to provide a particularly
simple and economical production of the shadowmask tubes for colour
television.
The tube according to the invention is characterized in that the
frame is formed with bosses for providing its contact in areas of
reduced cross-section, spaced from each other, with the mask
edge.
It has been established that with such a disposition, position
variations of the mask relative to the phosphors layer were smaller
than in the previously known tubes. It has even been established
that it was not then necessary to foresee fixation means of the
frame to the plate which should be specially adapted for
"adsorbing" the dilatations of the mask.
Moreover, the frame bosses increase the mechanical rigidity
thereof.
It is advantageous, particularly for reducing the size of the tube,
that the contact points between the mask edge and the frame are on
the inner periphery of said frame.
The invention relates also to a frame and to a mask for cathode ray
tubes.
Further objects, dispositions and advantages of the invention will
become more apparent from the description of one of its
embodiments, said description being made with reference to the
accompanying drawings wherein:
FIG. 1 is a schematic cross-sectional view, along line I--I of FIG.
2, of a portion of the mask and of the frame of the tube according
to the invention;
FIG. 2 is another schematic cross-sectional view according to a
plane perpendicular to the plate, of portions of the tube shown in
FIG. 1;
FIG. 3 shows the position of the fixation points of the mask to the
tube frame shown partly on FIGS. 1 and 2; and
FIG. 4 is a perspective more detailed view of a portion of the tube
according to the invention.
The colour television tube shown partly in the Figures comprises a
frontal portion or plate 1 (FIG. 4) on the inner face 1a of which
is deposited the phosphors layer of the tube. This plate 1 is
formed with an edge 2 for its connection with the conical rear
portion (not shown) of the tube.
Opposite face 1a is arranged a mask 3 which is made of a thin
metallic plate the thickness of which is of the order of 1/10th of
a mm, which is hollowed to form a grid of holes (not shown) and
which is formed with an edge 3a fixed to a profiled metallic frame
4 having the general shape of an angle iron with two branches 5 and
6. The edge 3a is fixed on the inner face (that is the face which
is turned towards the space delimiting the frame) of branch 6 of
said frame. Fixation means 7 are provided for jointing the frame
and therefore the shadow-mask to the edge 2 of plate 1.
The inner face of branch 6 of frame 4 is formed with bosses 8, 9,
etc. (FIG. 1) arranged at a distance from each other and regularly
on the periphery of the frame.
The contact between the edge 3a and the frame is provided only
through said bosses. The fixation of said edge to the frame is
effected by soldering points 10, 11 at the contact points of edge
3a with the bosses 8, 9.
In the example, the bosses are of a general rectangular shape and
are formed by snarling the branch 6 of frame 4.
Moreover, said bosses 8, 9 occupy but a portion of the width of
branch 6 (FIG. 2) which is closest to the branch 5. The branch 6
has therefore a half-width 6a in the vicinity of its free edge 6b
which is free of bosses and is at a distance from edge 3a.
In FIG. 3 has been schematically shown the general appearance of
the edge 3a of mask 3 with the fixation points of said edge 3a to
the branch 6 of frame 4 shown in the shape of crosses. There are
foreseen four fixation points 10, 12, 13 and 14 at the respective
apexes of the substantially rectangular shaped frame. Further
fixation points 15, 16, 17 and 18 are also provided in the vicinity
of the medium axes (mid-perpendicular lines) 19 and 20 of the sides
of the rectangle formed by edge 3a. However, the latter fixation
points are not exactly on said axes 19 and 20 but slightly shifted
relative to the latter and moreover they are not on the same side
relative to said axis. Thus, the fixation point 15 is on the right
hand side (in FIG. 3) of axis 20, whereas point 16 is on the left
hand side of the same axis 20. The points 17 and 18 are
respectively under and above axis 19. Finally, there is foreseen
further fixation points 11, 11a, 21, 21a which are respectively
between points 10 and 15, 15 and 12, 14 and 16, 16 and 13.
In the example, the longer diagonal of the mask having a length of
67 cm, the height of each boss is of 1.4 mm or more, their length
(the dimension along the longitudinal direction of branch 6) is of
25 mm or less, and the soldering points (for instance point 11,
FIG. 2), are at a distance of 3 mm or more from the free end 3b of
the mask edge. The distance between point 15 and axis 20 is of the
order of 6 mm; the point 16 is at the same distance from this axis
20. The points 17 and 18 are arranged at about 10 mm from axis 19.
Finally, points 11, 11a and 21, 21a are each at about 130 mm from
axis 20.
It has been established that with the disposition according to the
invention where the frame has the bosses and the edge 3a of mask 3
is only in contact with the frame or these bosses, along points
spaced from each other, and not on the whole periphery of the frame
or on bosses of the edge of the mask as in the previously known
tubes. Temperature variations of the mask now have minimum
consequences on the position of the latter relative to the plate.
It is believed that this result originates in the fact that, during
a temperature rise, the dilatations of the mask are absorbed by the
portions of edge 3a which are between the bosses. To this result
contributes also the fact that portion 6a of edge 6 of the frame is
spaced apart towards the outside from the edge 3a of the mask.
Moreover, the bosses improve the mechanical rigidity of the frame
4.
The reduction of the effects of the temperature variations on the
position of the mask relative to the plate permits to do away with
particular dispositions for the fixation of the frame onto the edge
2 of the plate, as is shown in FIG. 4.
For said fixation, the frame 4 is formed with couples of tongues 23
and 24 obtained from cuttings of branch 5 which are folded to form
a prolongation of branch 6, on the opposite side relative to branch
5. The tongue 24 is formed with two branches 25 and 26 separated by
a slot 27. Said branches 25 and 26 are in planes displaced one
relative to the other, so that the foreward face of branch 25 is
substantially on the same level as the rear face of branch 26, so
that the end 29 of a fixation lug 28 may be inserted between said
rear face of branch 26 and the foreward face of branch 25. The end
29 of the lug 28 is, moreover, soldered to the front face of branch
26. The lug 28 is also soldered to the rear face of tongue 23 and
the other end 30 of said lug 28 is fixed via a button 31 to the
edge 2 of plate 1.
The lug 28 is formed with two portions in parallel planes. Portion
28a terminating in end 30 is applied against the inner face of edge
2 of the plate whereas, as was discussed hereabove, the portion 28b
terminating in end 29 is applied by soldering points against the
tongues 23 and 24.
The lug 28 is a simple metallic blade without special means for
compensating eventual deformations caused by temperature
variations, said deformations being, as already mentioned,
compensated by the presence of the bosses of branch 6 of frame
4.
It is not indispensable that the bosses be made of snarled parts,
and as an alternative, said bosses may be protrusions of the
frame.
Preferably, the number of soldering points of the edge of the mask
onto the frame is at least equal to four, said four soldering
points being in the vicinity of the apexes of the rectangle formed
by said edge. For large dimension shadow-mask tubes as is the case
in the example described with reference to the Figures, the number
of soldering points is higher.
Finally, it is not indispensable that the mask edge be soldered on
all the bosses. Said edge may be in simple contact with some of the
bosses.
* * * * *